Exercise apparatus incorporating the use of weights attached to one end of a cable that passes over a system of pulleys to handles grasped by a user have been built in a number of forms for many years. This type of apparatus has been particularly popular for performing exercises to develop the upper body.
The first apparatus of this type included a cable passing over a single pulley with the user standing with either his back toward the pulley so that he could push on the handles to exercise his chest muscles or his chest toward the pulley so that he could pull on the handles to exercise his upper back muscles.
Motivation to add to the repertoire of exercise came from increased interest in body contact sports, particularly football, where greater strength of the shoulders and neck was desired for blocking and tackling.
A new type of upper body machine was disclosed in U.S. Pat. No. 4,757,992 to Heitsch et al for an apparatus in which the user sat on a bench with a backrest to stabilize the body while he grasped a handle in each hand with his forearms against pads and performed a hugging motion (brought his arms across his chest) to develop the muscles of the chest. The handles were on the end of a pair of levers whose resistance to turning was provided by a cam with the end of a cable attached to its periphery and whose other end passed over a pulley to an adjustable stack of weights sliding on a vertical track.
U.S. Pat. No. 4,844,456 to Habing et al discloses an exercise apparatus including one station with a seat and backrest and a lever with handles for pushing to perform presses from the chest The seat and back support are in a fixed vertical position on a vertical column however the inclination of the back support is adjustable. A second seat with backrest and pads for performing shoulder presses is provided.
In the type of exerciser described in the foregoing paragraphs, a common characteristic of the construction is slidable positioning of one member on another member such as when two tubes telescope together In such instances common practice is to detachably lock the two members together by devices known as popit pins. A popit pin is a pin that is slidably secured to one member and is spring loaded to pass engagingly into one of a plurality of holes in the second member. The popit pin is available from a number of sources including the Spartan Manufacturing Co., Grant Street, Santa Clara, Calif.
Another type of exerciser used to develop the arms and shoulders is the barbell used with an arm support at the elbows which stabilizes the arm while the user performs "curls". Stabilizing the arm in this manner confines the major stress (isolates) on the biceps.
The exercises described in the foregoing paragraphs illustrate that all around development of the arms and shoulders requires performing motions in a number of degrees of freedom and that, in any given exercise, the ability to stabilize part of the body, e.g., using a backrest to perform presses from the chest or elbow support when performing curls, is an important requirement to "isolating" on a particular muscle group in order to obtain maximum rate of strength increase.